As silicon semiconductors, magnetic devices, and so on have been manufactured in ever decreasing sizes and with ever increasing scales of integration, deteriorations of the device characteristics and reliability decrease have become greater issues. In recent years, in order to analyze defects in semiconductor devices in the nanometer regime and to locate and solve the causes of the defects in a fundamental manner in the course of development of novel processes and mass production, spectral analysis using (scanning) transmission electron microscopy ((S)TEM) and electron energy loss spectroscopy (EELS) and analysis of two-dimensional elemental distributions have become essential analytical means.
Electron energy loss spectra can be roughly classified into zero loss spectra in which no energy loss occurs in passing through the sample, plasmon loss spectra obtained by exciting electrons in valent electron bands and causing energy loss, and core loss spectra obtained by exciting inner shell electrons and causing energy loss. In a core loss spectrum, fine structures are observed near the absorption edges. The structures are known as energy loss near-edge structures (ELNES) and have information reflecting the electronic state of the sample and the state of chemical bonding. Furthermore, the energy loss values (positions of the absorption edges) are intrinsic to the element and so qualitative analysis can be performed. In addition, information related to the coordination around an element of interest can be obtained from shifts of the energy loss values known as chemical shifts. Consequently, a simple state analysis can also be performed.
In the past, in a case where an electron energy loss spectrum at a different location on a sample was obtained, the electron energy loss spectrum has been continuously acquired by combining a scanning transmission electron microscope for scanning a finely focused electron beam over the sample using scan coils with an electron spectrometer capable of spectral dispersion in terms of the amount of energy possessed by the electron beam and by spectrally dispersing the beam transmitted through the sample.
In the case of this technique, however, drift of the accelerating voltage of the electron beam caused by variations in external disturbances around the apparatus and variations in the magnetic and electric fields vary the aberrations in the electron spectrometer and the position of the origin of the electron energy loss spectrum. Therefore, it is difficult to compare the shapes of the energy loss near-edge structures of electron energy loss spectra at different measurement positions and weak chemical shifts.
Accordingly, patent literature 1 discloses that the focal position is made different between the x- and y-axes to thereby make the focal position on the x-axis and the focal position on the y-axis a spectral plane and an image plane, respectively, in contrast with a normal transmission electron microscope in which the focal positions on the x- and y-axes are placed at the same plane and a transmission electron microscope image is obtained.
As a result, all electron energy loss spectra of the sample in the y-axis direction can be separated and observed. In particular, an image obtained by a two-dimensional detector can be observed in such a way that the x-axis is an amount of energy loss and the y-axis is a spectral image 51 having positional information about the sample as shown in FIG. 16(b). The spectral image 51 is observed like a belt in a corresponding manner to lamination films observed with a transmission electron microscope (IEM) image 50 shown in FIG. 16(a). Consequently, electron energy loss spectra at different positions on the sample can be observed at the same time. The energy loss near-edge structures of electron energy loss spectra at different positions and weak chemical shifts can be compared in detail.